Landing, H2/H∞ control, glide slope, flare
The paper presents the automatic control of aircraft in longitudinal plane, during landing, by using the linearized dynamics of aircraft, taking into consideration the sensor errors and other external disturbances. Aircraft auto-landing is achieved by combining two control techniques: H2 and H∞ approaches; this way, a robust H2/H∞ controller is obtained. Within the robust H2/H∞ controller, the weights of the H2 and H∞ control techniques are adjusted such that the aircraft accurately tracks the desired trajectory during the two main stages of the landing process (glide slope and flare). The new automatic landing system also consists of: a subsystem which models the geometry of landing, providing the imposed value of aircraft longitudinal velocity and altitude, an optimal observer for the estimation of aircraft state and a dynamic compensator providing one of the two components of the mixed H2/H∞ control law. The theoretical results are validated by numerical simulations for the landing of a Boeing 747; the results are very promising and prove the robustness of the new auto-landing system even in the presence of disturbances.